Professional Terminology in the PCB Industry (A-C)

DDate Code Production DateRefers to the production date of the product, usually expressed in a 4-digit format (YY+WW), presented on the board through etching or printing, and typically displayed alongside the company logo and UL certification for identification or subsequent traceability.DES (Development–Etching–Stripping) is an abbreviation for development-etching-stripping, a process in the formation of circuit lines.

·Etching (蚀刻)‌: Uses etching solution (such as acidic or alkaline solutions) to remove exposed copper foil, leaving only the areas protected by the dry film.‌·‌Stripping (去膜)‌: Removes the remaining dry film layer, completing the transfer of the circuit pattern.‌Desmear Removing ResidueThe purpose of desmear is to remove resin residues and drilling debris, roughening the hole wall surface to increase the bonding strength between the hole wall and the copper layer to ensurePTH quality, and to ensure that the copper on the hole wall is connected to the inner copper for conductivity. The desmear process includes swelling, residue removal, and neutralization. For details, see【技术】Introduction to FPC Desmear ProcessDimple Dimple, DepressionThe degree of depression in blind holes refers to the extent of the depression on the surface of the hole after filling, with the development of the industry also introducing micro via filling processes, which can also useDimple to express the degree of depression on the hole surface.Dry Film (DF) Dry FilmDry film is a type of polymer material that, when exposed to ultraviolet light, undergoes a polymerization reaction, forming a stable substance that adheres to the board surface, thereby blocking electroplating and etching functions and forming precise circuit patterns on the copper foil.‌Dummy, Dummying Dummy Plating, DummyingDummy plating is a maintenance process used in the electroplating industry to remove heavy metal contaminants from the plating solution, named after the English term “Dummy.” This technique involves suspending large dummy plates in the plating solution for low current density electrolysis, causing heavy metal contaminants to precipitate on the electrodes. Dummy plates serve as maintenance tools for the plating solution and are often used in conjunction with activated carbon treatment to remove organic contaminants and metal impurities.EElectrodeposited Foil (ED Foil) Electrolytic Copper FoilElectrolytic copper foil is a thin film material formed by uniformly depositing a layer of metallic copper on a copper foil substrate through electrolysis, with a thickness typically ranging from a few microns to several tens of microns.Electroless Nickel/Immersion Gold (ENIG) Electroless Nickel Immersion GoldForms a nickel-phosphorus alloy layer on the copper substrate through chemical deposition, followed by a displacement reaction to plate a layer of gold on its surface. This process has excellent oxidation resistance, corrosion resistance, and high flatness, making it a common PCB surface treatment method.Elongation Elongation RateGenerally refers to the percentage of elongation of a metal under applied tensile force (Tension) until fracture occurs, relative to its original length.Etchback Back EtchingRefers to the process of removing resin,glass fiber substrate and other residues from the walls of through holes during multilayer board manufacturing through plasma or desmear etching, typically removing about 0.5 to 3 mils each time. This process is mainly used to improve theverticality andsurface roughness of through holes, ensuring the quality of subsequentcopper ring electroplating filling.Etch Factor Etching FactorThe etching factor is a key indicator of the quality of line etching, used to quantify the verticality of the line sidewalls and the uniformity of etching during the etching process. It is defined as the ratio of etching depth (usually the thickness of the copper foil) to the side etch width (half the difference in width of the conductor above and below), with the formula: etching factor = etching depth / side etch width. A higher etching factor indicates that the sidewalls of the lines are more vertical, with less side etching, resulting in better line precision and uniformity.Exposure ExposureExposure is the core step in the graphic transfer process, referring to the precise transfer of the designed circuit pattern from the film (negative) to the copper-clad board coated with photosensitive material (dry film or wet film) through ultraviolet (UV) light. The purpose is to define the precise circuit pattern for subsequent etching or electroplating processes.FFailure Analysis (FA) Failure AnalysisFailure analysis refers to the process of analyzing and studying the causes of failure or malfunction of a product or system. By collecting and analyzing failure samples, failure data, and related information, the goal of FA is to identify the root cause of the failure, explore solutions, improve product quality and reliability, and reduce the risk of failure.Film Film, Negative A key tool for graphic transfer, functioning similarly to a photographic negative, precisely transferring the circuit pattern to the copper-clad board through ultraviolet exposure. PCB negatives (films) are typically composed of a polyester base and a photosensitive emulsion layer, divided intopositive films andnegative films two categories.Flexible Printed Circuit (FPC) Flexible Printed Circuit BoardFlexible printed circuit boards are made from flexible copper-clad laminates (FCCL) and are characterized by their bendability, lightweight, and high-density wiring. Their core substrates are polyimide (PI) or polyester films, allowing for micron-level line realization through photolithography, with a thickness typically ranging from 0.07 to 0.4 millimeters.Flux Flux is a chemical substance used in the soldering process to facilitate the soldering process, protect solder joints, and prevent oxidation. Its main functions include removing metal surface oxides, reducing solder surface tension, and preventing re-oxidation during soldering. Flux typically contains the following components:·Film-forming agents (such as rosin): Prevents oxidation during soldering and forms a protective film after soldering.‌·Activators (organic acids): Dissolve oxides, but excessive amounts may increase corrosiveness.‌·Diffusion agents (such as glycerin): Improve solder flow, typically less than 1%.·Solvents (such as ethanol, isopropanol): Dissolve other components, form liquid soldering agents.